Non-ionic diisocyanate polyaddition products dispersed in polyethers of polyesters are already known. According to the teaching of German Auslegeschrift No. 1,168,075, diisocyanates are reacted with bifunctional primary alcohols in a dispersing medium consisting of a polyether or polyester (molecular weight 500 to 3000) containing at least two (exclusively secondary) hydroxyl groups in the molecule. According to German Auslegeschrift No. 1,260,142, compounds containing isocyanate and amino groups undergo a polyaddition reaction in situ in a polypropylene glycol ether dispersing agent. Non-ionic dispersions of polyurethanes, polyureas or polyhydrazodicarbonamides in polyvalent, higher molecular weight hydroxyl compounds obtained by the above mentioned processes are recommended as thickeners for the textile or dye industry because of their high viscosities even at low solids contents.
Thus a 10% (or 20%) dispersion of polyhydrazodicarbonamide in a polypropylene glycol ether obtained according to German Auslegeschrift No. 1,260,142 for example, has a viscosity of over 10,000 (or 200,000, in the case of a 20% dispersion) cP at 25.degree. C. This amounts to more than 10 (or 200, in the case of a 20% dispersion) times the viscosity of the pure dispersing agent. When attempts are made to prepare a 40% dispersion, the reaction mixture solidifies before polyaddition has been completed. The high viscosities which occur at even relatively low solids contents seriously restrict the possibilities of using the products because, in many fields of application, they cannot be dosed with the aid of the usual dosing apparatus. For producing polyurethane foams, for example, a purpose for which such dispersions could be used, the viscosities of the starting materials must be below 2500 cP when conventional high pressure machines are employed.